1. Field of the Invention
This invention relates generally to medical appliances; and more particularly to a special syringe for injecting liquids into or withdrawing liquids from a patient's body.
2. Prior Art
As is well known, there are myriad very important medical uses for syringes. It is also known in the medical community that a severe problem has developed in relation to all such devices.
That problem arises from the continuing presence of horrible diseases, particularly fatal and currently incurable diseases such as acquired immune deficiency syndrome ("AIDS") and hepatitis, transmitted by exchange of body substances between people. These diseases have led medical institutions to exclusively use disposable syringe needles for both injection and withdrawal of liquids from patients.
A severe residual risk remains, however, for medical personnel themselves in the inadvertent touching of needle tips after withdrawal from infected patients. Medical needles are designed and manufactured specifically to be extremely sharp and to puncture skin and flesh with only the slightest pressure.
As a result, what would ordinarily be an inconsequential scratch or pinprick can bring and has brought severe disease or even death to many medical staff members and others. Needless to say, health-care professionals are well aware of this risk and take considerable precautions to avoid such inadvertent punctures; thus the risk is reduced on a "probability" basis to an exceedingly small value.
Nevertheless, the exposure is so massive for working doctors, nurses and technicians that occasional punctures are inevitable. As a practical matter, it is virtually impossible for such an individual to reduce the incidence of accidental puncture to less than, say, one every year or perhaps one every few years.
Of course, not every such puncture follows contamination of the needle by a patient carrying a transmissible fatal disease. Nevertheless, there are enough medical personnel and enough such patients that a significant number of medical staffers die--and of course a greater number become very sick--from these accidents.
In discussion of this problem, needles of the types used with syringes commonly come to prominence. Though the word "hypodermic" has somewhat passed out of current usage in the medical profession, I shall for purposes of definiteness and simplicity refer to needles used with syringes for giving injections as "hypodermic needles". Needles used in drawing blood will be called "phlebotomy needles". By this terminology I mean to clearly distinguish all such needles from needles that are used for cannula insertion, the specific subject matter of my previously mentioned issued patent.
As detailed in that patent, the actual manual manipulations involved in using hypodermic and phlebotomy needles--as compared with cannula-insertion needles--are relatively favorable to avoiding puncture accidents. For that reason my first concern was for improvement of cannula-insertion needles.
The dangers of infection with hypodermic and phlebotomy needles nevertheless remain very important, partly because they are used in such enormous quantity. As noted in my patent, I did not mean to imply that hypodermic and phlebotomy needles are safe. There is an important potential for inadvertent unsheathing and many other kinds of accidents.
For example, as mentioned in my patent there are learning situations and emergencies, and circumstances in which the usual manual manipulations are complicated by patient mental or physical condition. While these situations are only a fraction of all instances of use of hypodermic and phlebotomy needles, this fraction nonetheless represents an enormous number of individual occurrences.
In a present-day standard, commercially available syringe, the needle is stainless steel, hollow, and extremely sharp at its frontal end. The shank of the needle is usually permanently fixed to a hub, which is screwed onto the frontal end of the syringe body so that the sharp end of the needle projects forward from the syringe body. The latter is a molded plastic cylinder, typically made of polycarbonate.
A plunger, or piston-and-handle combination, is fitted into the syringe body from the rear, and movably seals against the internal wall of the syringe body. In use, the plunger is first advanced fully.
Then, if the syringe is to be used for an injection, the needle is inserted into a supply of liquid to be injected; and the plunger is operated rearward to draw the liquid into the syringe body. The needle is then inserted into the patient and the plunger operated forward to expel the liquid into the patient.
If instead the syringe is to be used for withdrawal of liquid the needle is inserted into the patient's blood vessel--or in some cases into a body cavity abscess, or wherever fluid communication is to be established. The plunger is then operated rearward to withdraw blood or some other liquid from the patient as desired.
A separate safety cover is typically supplied in place on each needle. The separate safety cover firmly grips the needle hub and entirely covers the needle, to prevent accidental puncture and to prevent accidental contamination of the needle by substances in the environment, before use.
To use the needle, the safety cover must be entirely removed and set aside.
As already outlined, our focus of concern now shifts to the possibility that the needle may be contaminated by substances in the patient, during use. Accordingly the safety cover is to be replaced over the sharp end of the needle to prevent accidental puncture and, particularly, to prevent contact of people other than the patient, with possible contaminants on the needle.
It is here that the prior art fails to be effective, since the process of replacing the safety cover is subject to many risks of inadvertent mishandling as previously mentioned. The medical marketplace has seen various appliances and apparatuses aimed at solving this problem.
One such device is a special form of hypodermic needle, available commercially from the firm ICU Medical, Inc. under the trade name "ICU High Risk Needle". The ICU device is fitted with a sliding sheath that is carried on the shaft of the hypodermic needle itself. After use the sheath is advanced forward over the needle tip.
That device undoubtedly serves a useful purpose, and it is certainly not my desire to criticize what is apparently the only commercial effort directed to an important problem. On the other hand, that device evidently has limitations that should be mentioned.
First, the ICU High Risk Needle is offered as a special item at a special price, for use only with patients known to be "high risk" patients. Not all patients carrying transmissible fatal diseases are known to be high risks.
Secondly, the sheath is attached halfway out the needle, where there would appear to be potential for inadvertent application of lateral force with sufficient leverage to snap off the needle. If that should occur before the sheath were fully advanced, the potential for accidental puncture could be substantial.
Thirdly, it is not clear from commercial literature on the product that the sheath locks in place when advanced--or, if so, that it locks firmly enough to withstand normal jarring in the workplace. Without such a feature, the device would seem to offer very limited protection.
A number of patents have been issued for devices that shield medical needles. Among these is U.S. Pat. No. 4,592,744, issued June 3, 1986, to Janine C. Jagger et al. This patent illustrates and describes a device that facilitates retraction of a hypodermic needle into a personnel-protective enclosure--which also serves as a handle for the device. The Jagger patent also shows and describes another device that similarly facilitates retraction of a phlebotomy needle into a like enclosure. In both of these devices the retraction procedure is relatively cumbersome.
In the hypodermic device, the needle is mounted by a relatively tight press fit to the forward end of a syringe that is fitted within the handle. The needle also extends in a relatively loose press fit through a hole in the front of the handle.
After use, the entire syringe must be pulled bodily out of the back end of the handle, carrying the needle rearward out of its front-end press fit with the handle, and into the cavity within the handle. The needle is carried in a flange that is too wide to escape from the rear end of the handle, and accordingly is pulled away from its tight press fit to the front end of the syringe.
The needle is thus trapped within the handle. The user must then dispose of the handle (with enclosed needle) and syringe separately.
In the Jagger phlebotomy device, the blood-collection receptacle is initially enclosed within an outer housing/handle during use. The sharp rear end of the needle passes in a tight friction fit through an elastomeric stopper on the receptacle.
Thereafter the receptacle is used as a tool to unscrew the needle from the forward end of the handle. Then the receptacle stopper is pulled off the rear end of the needle, so that the receptacle with its blood sample can be removed from the handle. As the receptacle is withdrawn the needle is trapped by its flange in the handle.
Thus the two forms of the Jagger invention that are described require the user to pull the needle all the way back through the hole in the handle, until the needle is entirely within the handle cavity--and then either discard two different bulky pieces or engage in a compound motion to reconfigure the appliance before disposal.
The large-amplitude motion required to pull the needle into the cavity is generally awkward and requires use of both hands. It may be considered acceptable, if not fully desirable. The disposal of two large pieces and the compound motion, however, are both more distinctly undesirable.
Even more undesirable, in both the hypodermic device and the phlebotomy device, are Jagger's arrangements for arming the apparatus for retraction of the needle. By "arming" I refer to a process of discriminating between (1) operation of the device, for drawing blood or loading a syringe before injection; and (2) retraction of the needle, for disposal.
Syringe operation includes filling the syringe, by pulling outward on the plunger, either in drawing blood or prior to an injection. Phlebotomy-device operation includes moving each vacuum vial outward after it is full.
Thus, in Jagger's syringe and phlebotomy device alike, operation necessarily involves rearward motion of some kind. Retraction of course also involves rearward motion.
The apparatus must somehow be made so that it will not retract the needle during such operation, but will retract the needle after operation. Jagger uses two different arming philosophies in her two different devices.
The two philosophies actually are opposite, and as a result have opposite drawbacks. Both sets of drawbacks, however, are severe.
I shall first consider the Jagger hypodermic needle. In that device, proper syringe operation and proper retraction thereafter both depend upon maintenance of the design relationships between two friction levels.
To fill the syringe a user must first advance the plunger fully forward, insert the needle tip into the patient's blood vessel or into a liquid to be injected, and then pull the plunger back. In pulling the plunger back, it would be extremely unnatural and awkward for the user to grasp the very short protruding rear end of the syringe; rather the user will grasp the outer handle or enclosure.
Thus the user relies upon relatively high friction between the needle-carrying nosepiece and the front end of the handle to keep the assembly together during loading. After loading and emptying of the syringe are complete, however, the user relies upon relatively low friction between those same two parts to break the assembly down for needle retraction and disposal.
In essence, the device is supposed to be self-arming for retraction. The user does nothing to prepare for needle retraction after use, but rather depends upon the two friction levels to discriminate between loading and retraction.
The relationship between these two friction levels, however, is too easily upset. For example, they can be disturbed by temperature variations in storage, beyond the knowledge of the person using the device. They can also be disturbed by leakage of congealable or sticky substances such as blood or sucrose solution, through the large opening at the rear of the handle and into the exposed seams between the handle and the needle flange.
The necessary friction relationships can also be disturbed by imperfect insertion of the syringe tip into its mating receptacle at the rear of the needle flange. That procedure, which in many cases is performed by medical technicians on site, rather than the manufacturer's personnel, can at least in principle damage either of the friction-fitting surfaces involved.
In such circumstances the syringe can be extracted from the needle flange before the needle is retracted--leaving no proper means for retraction. Conversely, the syringe can become stuck in place in the handle, requiring relatively forceful efforts by personnel to separate the parts for needle retraction.
Besides being an annoyance, forcible separation may lead to accidental punctures, thereby defeating the purpose of the safety device. All of this is a natural result of Jagger's design, which attempts to avoid the necessity for a physical arming step on the part of the user.
Now I shall turn to the Jagger phlebotomy needle. Here an arming step is required, but the required step is unduly cumbersome.
A user must unscrew the flange of the phlebotomy needle--using the last vacuum vial as a driver--before pulling the flange and needle back into the handle. This arrangement for retraction is likely to be bothersome to busy medical personnel, and therefore even more adverse to reliable, safe operation.
In effect Jagger's patent illustrates two opposing philosophies for retraction arming. One may be said to represent an inadequate arming step, and the other an excessive arming step. Both, however, tend toward the same result--a relatively ineffective device.
Other prior patents describe devices for automatic or semiautomatic resheathing of hypodermic syringes.
U.S. Pat. No. 4,026,287 to Haller is among the better of these, since it at least provides for retraction of the used needle into a cavity in a unitary, sturdy structure. The Haller device, however, requires screwing the syringe plunger into the back of the needle flange after use, to destroy a frangible seal around the flange and then retract the needle.
Haller also fails to protect against inadvertent insertion of fingertips into the syringe barrel. Even more serious is the fact that Haller's syringe plunger can remain in place, held only by detents at the rear of the barrel.
The Haller plunger thus remains dangerously ready to drive the needle forward again if the syringe is accidentally jarred past the detents. In addition, Haller's device and most of the others discussed below are disadvantageous in that their after-use sheathing configurations are at least as long as--or in some cases longer than--the initial or before-use configurations.
A device to be discarded, particularly one that is dangerous if broken open, should not be so extended and should not have a multiple-stage structure. Such configurations invite breakage and potentially serious accident.
U.S. Pat. No. 4,631,057 to Mitchell also leaves the needle accessible to fingertips through the unsealed forward end of the sheath. Mitchell's device also shares with the Haller device an undesirable sensitivity to jarring the device out of its safety detents, and in addition a similar undesirable extended after-use configuration.
Other patented devices with a like vulnerability to jarring out of detents and a like extended postuse configuration, but at least providing better frontal shielding against fingertip insertion, are U.S. Pat. Nos. 4,573,976 (Sampson), 4,643,199 (Jennings, Jr. et al ) and 4,643,200 (Jennings, Jr.).
Worthy of mention for its provision of more positive resistance to jarring of the needle out of retracted position is U.S. Pat. No. 4,425,120 to Sampson et al. That device pays for its better safety locking with complexity of the manual manipulations required in use.
Similar observations apply to U.S. Pat. No. 3,890,971 to Leeson, which offers a relatively very compact and stable postuse configuration, but at the cost of a relatively complicated mechanism and large-amplitude motions to effect the resheathing.
Numerous devices for providing merely visual shielding or screening of hypodermic syringes have also been patented. Among these are U.S. Pat. Nos. 2,876,770 (White), 2,674,246 (Bower) and 3,134,380 (Armao). Such devices are actually counterproductive with respect to present purposes, since they effectively conceal the presence of a dangerously sharp and possibly contaminated needle.
Thus the prior art has failed to provide an optimum safety device for use under modern conditions in the field of the present invention. No prior-art device provides the necessary sure and easy operation that is essential to the effectiveness of such protection.